1. Field of the Invention
A stormwater filtration system having overflow/bypass capability forms the subject of the present invention. The stormwater filtration system includes a treatment container with a filter media that treats stormwater runoff through bioretention. Bioretention is the filtering of stormwater runoff through a terrestrial aerobic plant/soil/microbe complex to capture, remove, and cycle pollutants. The container includes a flow distribution tray, or flume, that includes a stormwater distribution compartment, or channel, and an overflow/bypass compartment separated by a dam wall or weir. The container receives stormwater through an inlet, and includes an overflow/bypass outlet pipe, as well as an underdrain pipe. The underdrain pipe receives the treated stormwater that flows downwardly from the distribution compartment through the filter media. The overflow/bypass outlet pipe receives primarily untreated stormwater attributed to high stormwater flow rates from the overflow/bypass compartment. The stormwater filtration system is particularly appropriate for receiving stormwater from building roof drain structures, such as vertically oriented drainage pipes that interconnect with the inlet.
2. Description of the Related Art
Stormwater bioretention treatment systems are known in the art. Such systems are described in U.S. Pat. Nos. 6,277,274 and 6,569,321, exclusively licensed to the assignee of this application, and incorporated herein in their entirety by reference. Such systems have been commercialized by Americast, Inc. and marketed under the FILTERRA® trademark. Further details of the FILTERRA® system may be obtained from the Americast, Inc. website at www.filterra.com. There, an article entitled “An Advanced Sustainable Stormwater Treatment System” authored by Larry S. Coffman and Terry Siviter is available that further describes a prior art FILTERRA® system. The article is also incorporated by reference herein.
The prior FILTERRA® system includes a substantially water impermeable treatment container having an underdrain pipe embedded near the bottom of the container. The container contains filter media, including a layer of mulch overlying a soil mixture. Live plants grow in the filter media and extend out through a top opening. The container is positionable below ground (albeit could be at, or above ground level) and typically located adjacent a roadway or parking lot where flow can occur through a cutout in the curb or otherwise through the filter media. Stormwater runoff from the roadway collects pollutants which are treated in the container. The underdrain pipe is connected to an outlet that flows into the storm sewer drainage system or a separate or adjacent infiltration system, either directly or first through a catch basin.
Stormwater runoff from building roof drains also results in stormwater pollution problems. Stormwater runoff from the roofs of buildings is drained through downspouts or through vertically oriented pipe systems directly into the ground where the pollutants can seep into the ground without treatment. A need has thus arisen for treating the stormwater runoff from building roofs.
Treatment of stormwater runoff at high flow rates also poses a problem. When the flow rates are high, in excess of the capacity of the stormwater treatment container, the excess capacities will simply overflow the treatment container. Thus, a need has arisen to permit high stormwater runoff to overflow or bypass the treatment container filtration media in a controlled manner.
One such solution for treating runoff from building roof drains and for treating high stormwater runoffs is described in commonly-owned U.S. Pat. No. 7,425,261, issued on Sep. 16, 2008, based on patent application Ser. No. 11/417,220, published as US 2007/0256966 A1 on Nov. 8, 2007.